Full‐Color “Off–On” Thermochromic Fluorescent Fibers for Customizable Smart Wearable Displays in Personal Health Monitoring

Abstract

Responsive thermochromic fiber materials capable of miniaturization and integrating comfortably and compliantly onto the soft and dynamically deforming human body are promising materials for visualized personal health monitoring. However, their development is hindered by monotonous colors, low‐contrast color changes, and poor reversibility. Herein, full‐color “off–on” thermochromic fluorescent fibers are prepared based on self‐crystallinity phase change and Förster resonance energy transfer for long‐term and passive body‐temperature monitoring, especially for various personalized customization purposes. The off–on switching luminescence characteristic is derived from the reversible conversion of the dispersion state and fluorescent emission by fluorophores and quencher molecules, which are embedded in the matrix of a phase‐change material, during the crystallizing/melting processes. The achievement of full‐color fluorescence is attributed to the large modulation range of fluorescence colors according to primary color additive theory. These thermochromic fluorescent fibers exhibit good mechanical properties, fluorescent emission contrast, and reversibility, showing their great potential in flexible smart display devices. Moreover, the response temperature of the thermochromic fibers is controllable by adjusting the phase‐change material, enabling body‐temperature‐triggered luminescence; this property highlights their potential for human body‐temperature monitoring and personalized customization. This work presents a new strategy for designing and exploring flexible sensors with higher comprehensive performances.

Electronic Skin for Health Monitoring Systems: Properties, Functions, and Applications

“…Reproduced with permission. [236] Copyright 2024, Wiley-VCH. c) Schematic illustration of self-powered real-time monitoring system of sweat i).…”

“…promptly process and visualize the signals collected by sensors. At present, there are mainly two visualization methods: to intuitively display color changes, [232][233][234][235][236] and to display on the screen through wireless communication technologies. [237][238][239] For example, Hou et al prepared a visualized fiber strain sensor using photonic crystals.…”

“…Ma et al developed thermochromic fibers that could be directly sewn onto clothing. [236] This reversible luminescence characteristic was generated by the reversible conversion of the dispersion state and fluorescent emission of fluorophores and quencher molecules embedded in the phase-change material during the crystallization and melting processes. When the body temperature rose from 37 °C to over 38 °C, the color of the fibers changed from green to red, indicating that the body was feverish and needed treatment (Figure 7b).…”

“…b) Photographs of a thermochromic sportwear at different body temperatures. Reproduced with permission [236]. Copyright 2024, Wiley-VCH.…”